3/4 to 1 pound asparagus 

salt and pepper 

Medium onion 

1/2 lb mushrooms 

1/4 cup olive oil 

1/4 tsp black pepper 

1 pound pasta 

1/2 cup freshly grated Parmesan cheese, plus more to taste

Snap off tough ends from the asparagus spears. Cut the spears in half lengthwise, then slice them on the diagonal into 1 inch pieces. Bring a quart of water and a bit of salt to a boil in a medium saucepan. Add the asparagus to the boiling water. Cook for 2 minutes, drain the asparagus, and reserve 1/4 cup of the cooking liquid. Set the asparagus and cooking liquid aside separately. Peel and dice the onion. Thinly slice the mushrooms and set them aside. Heat the oil in a large skillet. Add the onions and saute over medium heat, stirring occasionally, about 10 minutes. Add the mushrooms, raise the heat to medium-high, and saute until they have softened and thrown off their juices, about 5 minutes. Add salt and pepper to taste. Add the asparagus and reserved cooking liquid to the skillet. Simmer until the asparagus is heated through and the sauce has thickened a bit, about 2 minutes. Taste for salt and pepper and adjust if necessary. While preparing the sauce, cook and drain the pasta. Toss the hot pasta with the asparagus and 1/2 cup of Parmesan. Mix well and transfer portions to warm pasta bowls. Serve immediately, with more grated cheese passed separately.